Use generics to avoid context casting

[Ragmaanir]

Hi, im using your shard in a private project and so far it works great (errors in fields are little difficult to track down though). A thing that is a bit annoying is the casting of the context in every field. Would it be possible to make the Schema-class or the ObjectType-class generics so one does not need to cast the context?

[ziprandom]

hey, sorry for the late answer. I will look into this as soon as I fix the shard (and more importantly it's dependency cltk) for the latest crystal release (0.24.1).